The current study is designed to test how treatment with ddI + 3TC or d4T + 3TC compare to each other and to ZDV + 3TC therapy as measured by antiviral effect, immunologic effect and resistance development. In addition, ddI + 3TC and d4T + 3TC will be compared to ddI and d4T monotherapy respectively using the same measures. The comparison with monotherapy will occur only over the first 24 weeks of the study after which time all patient will receive either ddI, d4T or ZDV in combination with 3TC.